It is to be understood that the present invention relates to generators as well as to motors, however, to simplify the description that follows, a motor will be described with the understanding that the invention also relates to generators. With this understanding, there are two types of interior permanent magnet motors (IPM motors). In one type, the magnets lie orthogonally to the air gap between the rotor and stator, like spokes. In the other type, called circumferential IPM motors, the magnets face the air gap. Rotors for circumferential IPM motors have typically been made with stacked stamped steel laminations and circumferentially extending permanent magnets embedded in the interior of the laminations. These circumferential IPM motors utilize narrow bridges, slits and air spaces within the rotor to substantially reduce the flux leakage that occurs and that would occur to a debilitating degree if these features were not incorporated into the rotor lamination design. These features greatly weaken the rotor, not allowing it to rotate at medium high and high speeds, and still do not fully eliminate the flux leakage.
There is thus a need to develop a circumferential type IPM machine having a structurally robust rotor operable at medium high and high speeds with minimal rotor flux leakage, and preferably that may be produced at a lower cost than that of currently fabricated IPM machines.